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Authors:

Carl Jonsson (The University of Melbourne, Australia), Tesfaye Molla (The University of Melbourne, Australia)

Abstract:

Interest in the field of alternate binders for WC hardmetals has increased due to the health implications surrounding the use of cobalt as a binder material. Here, an Integrated Computational Materials Engineering (ICME) approach was used to search for alternate binder compositions using a reduced order model. The model was derived by combining the densification mechanisms present in cobalt containing compacts with the rate enhancing factors governing early onset densification. The model incorporates thermodynamic and kinetic components coupled to a multi-objective genetic algorithm. It allows alloys with compositions optimized for sintering to be ranked against those optimized for mechanical properties to form Pareto sets. By incorporating the sinterability and mechanical properties of the system simultaneously, alternatives that are manufacturable using existing procedures can be determined.

DOI:

https://doi.org/10.59499/WP225371931

Authors:

Oliver Levano Blanch (The University of Sheffield, United Kingdom), Beatriz Fernandez Silva (The University of Sheffield, United Kingdom), Martin Jackson (The University of Sheffield, United Kingdom)

Abstract:

Titanium alloys are well known for their high strength to weight ratio. However, its use is restricted in many sectors simply due to its high cost when processed through the conventional route. Powder metallurgy has been proven as an alternative way to reduce the cost of near-net shape titanium components. The cost of powder is related to its source, but technologies like additive manufacturing (AM) produce large quantities of surplus powder that can be reused with alternative technologies. Alternatively, the option to use titanium machining swarf as a feedstock material is also explored to further reduce the price of titanium components.In this work, Ti-6Al-4V swarf and surplus AM powder has been consolidated using field-assisted sintering technology (FAST) and hot isostatic pressing (HIP). The consolidation, microstructure and hardness has been assessed to explore and compare the potential of these technologies in the production of low-cost titanium near-net shape parts.

DOI:

https://doi.org/10.59499/WP225372019

Authors:

Masaru Kawakami (Fujidie Co., ltd, Japan) Sota Terasaka (Tohoku University, Japan)

Abstract:

Phase diagrams of C-Co-W-M (M: V, Ti, Ta, etc.) quaternary system were drawn using software for thermodynamic calculation in multicomponent systems. Pseudo-ternary phase diagrams of triangular prism were constructed by superimposing the Co-WC-MC sections of the tetrahedral quaternary phase diagram for each temperature. The vertical sections with a constant content of Co for the triangular prismatic diagram showed pseudo-binary phase diagrams of (MC-Co)-(WC-Co). The pseud-binary phase diagrams revealed constituting phases during sintering and solubility limits of metal carbides in solid and liquid Co phases. Formation of segregated phases of metal carbides for specified amount of the metal carbides was considered using the pseud-binary phase diagrams.

DOI:

https://doi.org/10.59499/EP256767708

Authors:

Louise Rosenblad (1), Per-Lennart Larsson (1), Henrik Larsson (2), Hjalmar Staf (1,3)

1- Department of Engineering Mechanics, KTH Royal Institute of Technology, Sweden

2- Department of Materials Science and Engineering, KTH Royal Institute of Technology, Sweden

3- Sandvik Coromant AB, Sweden

Abstract:

During sintering, a green body of powder particles is heated to high temperatures, fusing the particles together. In cemented carbide production, the sintering process generally results in substantial densification of the material. By using a dilatometer, shrinkage during the sintering process can be measured. For a green body of lower density, early particle rearrangement has been observed. This is investigated here using different initial densities using the same powder, leading to a suggested addition to the constitutive model. The environment in the dilatometer and the sintering furnace differs, especially with respect to heating and temperature during holding. This effect can be minimized by creating robustness in the model, making it independent of the heating cycle. Here, this is done by optimizing the constitutive parameters towards four heating cycles for a specific powder.

DOI:

https://doi.org/10.59499/EP246275377

Authors:

Louise Rosenblad (KTH, Sweden), Per-Lennart Larsson (KTH, Sweden), Henrik Larsson (KTH, Sweden)

Abstract:

From a previously developed constitutive model of cemented carbide, the powder size- and configuration can be used to simulate the densification during the sintering process. However, small differences in experimental execution cannot be accounted for in the simulation, making the model sensitive. Here, we study how well the developed constitutive model can capture the experimental results of a dilatometer test. Three different experiments were performed where the only difference was the transition between the debinding and sintering process. From parameter adjustments, it is seen that the constitutive model is more suited to a certain experimental setup, which is a limitation of the model.

DOI:

https://doi.org/10.59499/WP225372032

Authors:

Oliver Schenk (1), Yuanbin Deng (1), Anke Kaletsch (1), Christoph Broeckmann (1)

1- RWTH Aachen University, Institute for Materials Applications in Mechanical Engineering (IWM), Augustinerbach 4, 52062 Aachen, Germany

Abstract:

The powder metallurgical (PM) process chain stands out by its ability to produce precise components at low cost. However, the inherent porosity of PM components, which has a particular impact on fatigue behavior, is crucial for components such as gears. Hence, cold rolling is commonly applied to densify the surface of sintered components. This induced densification can be modelled by a constitutive law introduced by Gurson, Tvergaard and Needleman. In this work, a modified GTN model was derived to simulate the densification behavior of Astaloy 85Mo sintered steel. The stress-strain-behavior of sintered samples with different densities was deduced from compression tests according to Rastagaev. A synthesized description of the plasticity of the dense material was then combined with the densification behavior during compression to obtain a density-dependent GTN model. The model was validated by comparison with experimental data on the densification during sizing and cold isostatic pressing of sintered samples.

DOI:

https://doi.org/10.59499/EP235763767

Authors:

Daniel Figueiredo (1,2), B. Guimarães (1,3), Tiago E.F. Silva (4), Cristina M. Fernandes (1), J. Paulo Davim (2)

1- R&D Department, Palbit S.A., Aveiro, Portugal

2- Department of Mechanical Engineering, University of Aveiro, Portugal.

3- Center for MicroElectroMechanical Systems, University of Minho, Guimarães, Portugal

4- INEGI, University of Porto, Porto, Portugal

Abstract:

Machining in ductile mode is usually applied for finishing precision parts of hard materials, such as cemented carbide parts, medical ceramic components or glass material applications. Thus, the study of ductile mode cutting of brittle materials has been attracting more and more efforts. The possibility of applying predominant plastic-flow cutting (ductile mode), using ultra-precision machines, in hard/brittle materials has been previously linked to the careful selection of operational conditions, regarding the brittle-to-ductile threshold. This threshold, also known as the critical depth of cut, relates with material specific properties (i.e., elastic modulus, material hardness and fracture toughness) as is widely employed in grinding processes control. In the present work, micro-milling of WC-15wt.%Co sintered samples was performed with diamond coated end mills, confirming the influence of a ductile-to-brittle threshold on the cutting regime. Critical scale effects and structure-related behaviour were also confirmed. A positive impact on machined surface quality was observed when ductile mode was applied. Scanning electron microscopy was used to evaluate the microstructure features after different machining conditions.

DOI:

https://doi.org/10.59499/EP246281747

Authors:

Tuomas Jokiaho (1), Atte Antikainen (1), Juha Lagerbom (1), Tomi Lindroos (1), Elina Huttunen-Saarivirta (1)

1- VTT Technical Research Centre of Finland Ltd., Finland

Abstract:

Nitrogen-alloyed austenitic nickel-free stainless steels (ANFSS) are known for their good corrosion resistance and mechanical properties, and stable non-magnetic nature. As long as the nitrogen content remains within certain limits, increasing the nitrogen content generally improves all the said properties. However, if the nitrogen content is increased up to a too high level, ductile-to-brittle transition may take place. The optimal nitrogen level is determined by other alloying elements that can have a role in stabilizing the austenite and increasing nitrogen solubility in the melt during manufacturing. In this research, we investigate how to control the nitrogen content of nominally Fe-16Mn-14Cr-0.27C-0.35N steel during direct energy deposition processing using the mixtures of powders representing the nominal composition and subjected to a nitriding treatment. An emphasis is placed on the corrosion and mechanical properties of the resulting alloy, which we aim to explain by the analyses of material chemical composition and microstructure.

DOI:

https://doi.org/10.59499/EP246281583

Authors:

Giuseppe Vecchi (1), Eleonora Atzeni (1), Luca Iuliano (1), Alessandro Salmi (1)

1- Politecnico di Torino, Department of Management and Production Engineering (DIGEP), Corso Duca degli Abruzzi 24, 10129 Torino, Italy.

Abstract:

Recent improvements in the Laser Powder Directed Energy Deposition (LP-DED) process for repair applications shift the focus to the analysis of possible alterations in the substrate, which is subjected to repeated thermal cycling during deposition of the material. In general, thermal loads can be controlled by changing process parameter. In this work, a two-step bi-directional spiral deposition strategy, alternating between deposition from inward to outward and backfill, is analyzed to evaluate the heating of the substrate and the resulting porosity of the added material. The outcomes indicate the potential of this strategy to control heat flow and achieve a more uniform thermal field. Porosity is minimized by optimizing the hatch spacing, and benefits are observed also in terms of top surface roughness.

DOI:

https://doi.org/10.59499/EP235762610

Authors:

Sasha Cegarra (1), Jordi Pijuan (1), María Dolores Riera (2)

1- Eurecat, Centre Tecnològic de Catalunya, Unit of Metallic and Ceramic Materials, Plaça de la Ciència 2, 08243, Manresa, Spain

2- Department of Mining, Industrial and ICT Engineering, Technical University of Catalonia-(UPC), Av. De les Bases de Manresa, 61-73, 08242, Manresa, Spain.

Abstract:

Centrifugal atomization technique to produce metal powder offers many advantages in terms of spherical morphology of the powders, high production yield and narrow particle size distribution. Centrifugal atomization is also considered a rapid solidification technique. The final microstructure of the atomized particles is closely linked with the thermal history and cooling rates experienced during the atomization process. In this work, Al-4%Cu alloy was atomized via centrifugal atomization under different atomization conditions. Gas composition and melt superheat temperature were investigated as processing parameters that influence in the cooling history of the atomized droplets. Cooling rate was experimentally evaluated by means of the Secondary Dendrite Arm Spacing (SDAS) technique using four measurement methods found in the literature, and a numerical model was implemented to study the heat transfer between the droplets and the surrounding gas once the particles have been expelled from the disk, to identify the correlation between theoretical and experimental results.

DOI:

https://doi.org/10.59499/EP235765262

Authors:

Pavel Ctibor (1), Libor Straka (2)

1-The Czech Academy of Sciences, Institute of Plasma Physics

2-Czech Technical University, Faculty of Electrical Engineering

Abstract:

Commercial powders made of two copper oxides were compacted with spark plasma sintering (SPS). Their dielectric properties were studied in a broad range of frequencies and temperatures. Various relaxation phenomena were documented. DC resistivity was measured as well. Microstructure and phase composition were studied, and phase purity was shown for CuO, whereas Cu2O was more sensitive to carbon contamination during the SPS processing. Influence of the sintering temperature on microstructure and electrical properties was described for both materials.

DOI:

https://doi.org/10.59499/EP246276957

Authors:

Thomas Hutsch (1), Sebastian Riecker (1), Marvin Uhlig (2), James Siegenthaler (2), Matthias Mühle (2), Thomas Studnitzky (1), Johannes Trapp (1), Thomas Weißgärber (1, 3)

1- Fraunhofer IFAM Dresden, Dresden, Germany

2- Fraunhofer USA, Michigan, USA

3- TU Dresden, Dresden, Germany

Abstract:

Many requirements and applications in various industrial sectors demand high-quality finishes on parts. These finishes, whether due to tolerances or surface quality, are often challenging to achieve through additive manufacturing technologies, necessitating additional post-processing. This study aims to investigate the effect of specific surface treatments on parts produced through Sintering Based Additive Manufacturing (SBAM), such as Fused Filament Fabrication (FFF). With the premise of employing affordable post-processing methods that can potentially maintain competitive prices for the parts, the study analyzes the post-processing techniques of shot blasting and vibratory polishing on parts with different geometries. Additionally, the study examines the effect of surface treatments on part walls manufactured at various angles. The results obtained demonstrate significant improvements in surface roughness, although there is potential for them to modify the geometry and round the edges of the parts.

DOI:

https://doi.org/10.59499/EP246283253